Metal-amine-complex in geiger counter



April 17, 1962 T. A. cHUBB METAL-AMINE-COMPLEX 1N GEIGER COUNTER Filed May 16, 1958 R m WB m BUD H C A. MIHHHH T IMm O ym A T .E t f mm m. vl.

U NN N E Ek HWF United States Patent Oiiice 3,030,537 Patented Apr. 17, 1952 3,030,537 METAL-ANHNE-COMPLEX lN GEIGER COUNTER ralbot A. Chubb, Forest Heights, Md.

(319 Onondaga Drive, Washington 21, D C.) Filed May 16, 1953, Ser. No. 735,909 7 Claims. (Cl. 313-93) (Granted under Title 3S, U.S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties vthereon or therefor.

This invention relates to a Geiger-Mueller counter and in particular to a Geiger-Mueller counter whose operation is not affected by long periods'of counting.

Basically all self-quenching counters contain an admixvture of an inert gas such as argon, neon, or helium and a quenching agent, usually a polyatomic organic compound that effectively suppresses secondary electron emissions at the cathode. The suppression of secondary electrons is of extreme importance in Geiger tubes, for secondary electron emission causes the discharge to continue indefinitely after the main ionizing event has been cleared out of the tube. After an electron discharge has occurred, the positive ions travel outward to the cylinder and there draw electrons out of the cathode surface and become neutralized. Upon returning to the ground state, however, neutralized atoms of argon, neon, or helium release their recombination energy in the form of ultraviolet photons. The principal role of the polyatomic quenching agent is to prevent the release of ultraviolet photons by dissociating or decomposing its own molecule thereby dissipating the photon energy in the dissocation process that otherwisercontributes secondary electrons to the discharge, i.e., polyatomic molecules are photonquenching. Thus, a single sharp pulse rather than a continuous discharge is obtained from a counter filled with an admixture of inert gas and an organic vapor.

Self-quenching counters, however, suffer from decompositionof the organic quenching vapor with continuous use; the counter undergoes changes in the operating characten'stics, that is, the operating voltage increases, the plateau shows a considerable slope, and a longer recovery time develops which decreases the counting rate of the tube. In time all the large organic molecules are decomposed into simpler products that may be of little or no quenching value in the counting process. The performance of the counter is also affected by decomposition products which combine to form dielectric polymer films on the cathode and anode surfaces thereby interfering with the discharge.

Quenching gases and vapors have been selected in the past on the basis of their chemical stability, in that no reaction should occur in the gaseous filling of the tube nor between the quenching vapor and the metal electrodes. Any interaction in the counter space meant, in all events, the removal of quenching vapor from the tube space or the formation of new molecules which were not in themselves adequate for the quenching process. Reactions of these types have been regarded as contributing to an irreparable loss of quenching medium. In the present invention7 a reactive gas is advantageously combined Vwith a metal surface whereby the gaseous components in the tube are maintained at the optimum level and any decompositions and recombinations that may be occurring in the gaseous components do not affect adversely the operation of the counter.

It is therefore an object of the present invention to provide a novel Geiger-Mueller counter having extreme Y stability and an unusually long operable life.

Another object of this invention is to provide a novel Geiger-Mueller counter which is capable of passing a large number of counts without any noticeable deterioration in the quenching vapor.

A further object of this invention is to provide a counter tube which retains a certain portion of the quenching medium in reserve so that it becomes available to the counting operation after the counter has been in operation for a period of time.

A still further object of this invention resides in a Geiger-Mueller tube which is capable of a long continuous operation without loss of eiciency or in operating voltage.

lOther objects and features of the present invention will become apparent from the following detailed description when considered with the drawings in which:

FIG. l is a longitudinal section of a Geiger-Mueller tube which incorporates the novel features of the pres lent invention;

a further alternate embodiment of the invention.

In general with the teachings of the present invention, a VGeiger-Mueller tube of the self-quenching type contains in the gaseous filling an inert gas such as argon, neon, or helium and a chemically active gas, preferably an organic amine such as methylamine, ethylamine, etc., in relatively small percentages. The chemically active gas is added initially in an amount sufr'icient for a portion of it to combine with a metal, preferably copper or silver, to form a metal complex. By a metal complex is meant any nature of association of the metal with the reactive gas molecules to form an ionic type complex or a Werner type coordination complex, but the nature of this association is immaterial for the successful practice 'of the present invention.

It has been determined as a result of this invention that counters containing organic amine-inert gas admixtures are capable of operating for long periods under sustained counting without any noticeable deterioration of the amine gas or vapor present in the tube. 'The counter is capable of a sustained operation without requiring any storage or resting period in order to regenerate the amine. Furthermore, the operable life of the tube is considerably increased by providing for an amine reservoir: The amine reacts with a metal to form a metal-amine-complex that is suiciently stable to remain on the metal surface during the early life of the tube. After the tube has been in operation for a period of time, the metalarnine-complex decomposes slowly, thus providing for a fresh supply of organic amine to replace any loss of quenching agent resulting from the operation of the tube. In this way, the gaseous admixture is retained at or near the optimum concentration, and the counter does not experience any of the usual symptoms of aging due to loss of quenching agent.

Referring now to the drawing, the Geiger-Mueller tube shown in FIG. 1 comprises a cathode cylinder 11 composed of copper and forming a portion of the tubes envelope; the cylinder is coaxially arranged with respect to an anode wire 12 composed of substantially pure tungsten. The anode wire is centrally located within the metal envelope and insulated therefrom at each end by any suitable means such as ceramic end portions 13 which also confine the enevelope space 14, the ceramic end portions being sealed to the cathode cylinder 11 with an epoxy resin cement, shown at 15, or any other suitable means. The anode wire is soldered to a metal cap 16 at one end while a wire support terminal 17 supports the anode wire at the other end through the use of a metal bead 18 which is soldered to the anode wire and passed through sl-itted opening 19 in the wire support terminal. The wire support terminal extends through ceramic end portion 13, the exterior portion of the metal forms a threaded ring 21 which provides a means for attaching a protectivecap (not shown) over the glass seal 22. Gas outlet tube 23, made of glass and sealed to the wire support terminal 17 with a fused powdered glass, provides a means for evacuating and filling the counter. The gas outlet tube after evacuation and filling with the desired gaseous components is sealed by melting the end of the glass to form glass seal 22. A The copper cathode Geiger-Mueller tube described herein is considerably improved in its quenching properties by adding a small amount of an organic amine such as methylamine gas, ethylamine, ethylenediamine, etc., to the gaseous lling of the tube. A typical gaseous admixture suitable for the purposes of this invention is millimeters Hg of methylamine gas and 400 millimeters Hg of argon; the gaseous admixture is introduced into the tube by any `convenient means. After the ytube has been filled with the gaseous admixture, suicient time should be allowed for the amine to react or complex with the copper cathode; the surface thereof receives a bluish tint as the amine reacts or complexes with the copper metal. A sensitive manometer attached to the glass tube output 23 will indicate a reduction in the internal pressure when the amine has been removed from the space as a result of the chemical reaction. The amine is introduced in sufficient amount to provide for the copper-amine-complex to form on the cathode surface and also to provide for an additional amount of amine in the gaseous filling to serve as quenching agent in the operation of the tube. The metal complex forms a reservoir of amine gas which decomposes slowly during the operation of the tube to provide` for an additional supply of amine gas.

The copper-amine-complex on the cathode surface does Vnot affect the sensitivity of the Geiger counter which responda to radiation of wavelength less than 1 angstrom and to charged particles of energy greater than 500,000 e'v. -For such radiations the response of the'counter is unaffected by the thin surface complexes as provided for by the present invention. o As aresult of the copper-amine-complex cathodesurface and the methylamine-argon gas admixture, the Geiger- Mueller counter is considerably stabilized. It is capable of a long continuous operation Without loss of efliciency and without change in the operating voltage. yIt is unaffected in its counting operation even after 109 counts whereas counters with other organic quenching agents tend to go b ad long before that many counts are passed through the tube. The operatingl voltage remains very nearly constant even after fourmonths of sustainedcounting.

Geiger-Mueller counters may be constructed in accordance with this invention using other organic amineinert gas admixtures: An ecient quenching agent is the diamine type of molecule. For instance, a counter may be filled with 6 millimeters Hg of ethyenediamine and 250 millimeters Hg of helium to give a satisfactory counting operation and an operable lifetime which is not limited to the deterioration rate of its quenching vapor. The diamine vapor may vary in these admixtures from about 3 to 8 millimeters while satisfactory counters have been constructed with the inert gas present from amounts of about 2.50 to 800 millimeters. Other amines such as methylamine land ethylamine have been used in amounts from about 5-25 millimeters although other amounts of amine may be used depending of course on the size of the counter. Y

ln the theoretical treatment of the present invention, an organic amine quenching agent in combination with the metal-amine-complex cathode surface in a Geiger-Mueller tube having an exceptionally long and stable life suggests that decomposition which may be talringV place in the gaseousl filling does not alect the characteristics of the tube.. It may be assumed that any new products that do form in the4 gaseous lling may also have quenching properties. It is also apparent that no deposition of polymer-like coatings form on the cathode surface, in fact, any chemical reaction occuring on the cathode surface is in the nature of an equiiibrium in the formation of metal-amine-complex and amine gas or vapor. The ability of the quenching gas to maintain a very nearly constant partial pressure in the gaseous lling is due to a replenishment of the gas by the slow decomposition of the metalamine-complex from the cathode surface. As the quenching agent is undergoing rearrangement or decomposition, the amine is slowly being Ireleased from the cathode surface to provide a fresh supply of quenching medium. The lifetime of the tube is further aided by the fact that any deterioration products that form in the operation of the tube are not deleterious to the counting process.

A further embodiment of this invention is shown in Y FIG.. 2 in which the Geiger-Mueller counter has a cathode,

formed of a metal such as chrome-iron which does not react readily or form a complex with an organic amine. The metal cathode in this instance does not form a metal'- arnine-complex in the presence of an organic amine gas or vapor. ln this counter, a glass bulb 24 is shown containing copper or silverin the form of gauze 25, sponge, or any other form of the metal which has an increased surface area; the copper or silver is reacted with an orgarlic amine to form metal-amine-complex, which is retained in the glass bulb and which becomes available to the counter space during the operation of the tube. As

Vthe quenching agent in the tube is being altered or consumed, the metal-amine-complex in the glass bulb decomposes slowly to release a fresh supply of amine in the tube space. The metal-amine-complex reservoir 24 is positioned in such a manner that it will not interfere with the counting process in the tube. The metal reservoir is preferably positioned as shown in FIG. 2, in the gas outlet tubeY away from the tube space. In an alternate embodiment, the cylinder may have a small opening in the metal wall through which a reservoir can communicate with the tube space. The metal gauze or sponge metal may be re- -acted initially with the amine,kand the bulb may then be connected to the counter, or else the tube space and bulb .attachmentmay receive the amine vapor in a single step, Ywhere a portion of the amine reacts with the metal in the bulb and the remaining portion of amine serves as quenching agent in the tube space.

Y The metal-amine-complex in each of these embodiments supplies additional quantities of quenching vapor which increases the operable life of a Geiger-Mueller counter. The amine vapor does not break down into contamination Yproducts to form dielectric coatings on the cathode surface which heretofore has resulted in lower eciency and loss of operating voltage. YAs a result of this invention the `Geiger-Mueller counter does not suffer from loss of quenching medium which in the past has been a detervmining factor in the operable lifetime of a Geiger-Mueller tube.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that Within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A Geiger-Mueller counter tube comprising a metal envelope which serves as the cathode, a coaxial anode, a gaseous filling therein, said gaseous lling containing an inert gas and a chemically active gas which serves as quenching agent, and a reservoir in communication with said gaseous filling for containing a portion of said chemically active gas in reserve as a metal-complex.

2. A Geiger-Mueller counter tube comprising an envelope having a metallic inner surface which serves as a cathode, a coaxial anode and a gaseous filling therein, said gaseous filling containing an inert gas and a chemically active gas which serves as quenching agent, said chemically active gas being reactive with said metallic inner surface to form a metal-complex therewith.

3. A Geiger-Mueller counter tube comprising an envelope having a metallic inner surface which serves as a 5 cathode, a coaxial anode and a gaseous filling therein, said gaseous filling containing an inert gas and an organic amine, said amine being reactive with said metallic inner surface to form a metal-amine-complex therewith.

4. A Geiger-Mueller counter tube as claimed in claim 3 in which the amine is methylamine.

5. A Geiger-Mueller counter tube as claimed in claim 3 in which the amine -is ethylenediamine.

6. A Geiger-Mueller counter tube comprising an envelope having a metallic inner surface which serves as a cathode, a coaxial anode, a gaseous filling therein, said gaseous filling containing an inert gas and a chemically active gas which serves as quenching agent, and a reservoir in communication with said gaseous filling, said reservoir adapted to contain a metal-complex whereby said metal-complex decomposes slowly to replace chemically active gas which is consumed during the operation of the counter tube.

7. A Geiger-Mueller counter tube comprising an envelope having a metallic inner surface which serves as a cathode, a coaxial anode, a gaseous filling therein, said gaseous filling containing an inert gas and an organic amine, and a reservoir in communication with said gaseous lling, said reservoir adapted to contain a metal-aminecomplex whereby said metal-amine-complex decomposes 5 slowly to replace the airline which is consumed during the operation of the tube.

References Cited in the le of this patent UNITED STATES PATENTS 10 2,521,315 Vctoreen Sept. 5, 1950 2,599,352 Schneider June 3, 1952 2,654,041 McCurdy et al Sept. 19, 1953 2,714,680 Warmoltz et al Aug. 2, 1955 2,873,399 Garrison Feb. 10, 1959 15 2,921,217 Chubb Jan. 12, 1960 OTHER REFERENCES lElectron and Nuclear Counters, by Kortf et al.; D. Van Nostrand Co., Inc., 1955, second edition, pages 173 20 and 174. 

1. A GEIGER-MUELLER COUNTER TUBE COMPRISING A METAL ENVELOPE WHICH SERVES AS THE CATHODE, A COAXIAL ANODE, A GASEOUS FILLING THEREIN, SAID GASEOUS FILLING CONTAINING AN INERT GAS AND A CHEMICALLY ACTIVE GAS WHICH SERVES AS QUENCHING AGENT, AND A RESERVOIR IN COMMUNICATION WITH SAID GASEOUS FILLING FOR CONTAINING A PORTION OF SAID CHEMICALLY ACTIVE GAS IN RESERVE AS METAL-COMPLEX. 